Tracking Generator (Models 13, 16 and 28) R&S FSL
1300.2519.12 4.136 E-11
Calibration mechanism
Calibration means a calculation of the difference between the currently measured power and a
reference curve, independent of the selected type of measurement (transmission/reflection). The
hardware settings used for measuring the reference curve are included in the reference dataset.
Even with normalization switched on, the device settings can be changed in a wide area without
stopping the normalization. This reduces the necessity to carry out a new normalization to a minimum.
For this purpose the reference dataset (trace with 501 measured values) is stored internally as a table
of 501 points (frequency/level).
Differences in level settings between the reference curve and the current device settings are taken into
account automatically. If the span is reduced, a linear interpolation of the intermediate values is applied.
If the span increases, the values at the left or right border of the reference dataset are extrapolated to
the current start or stop frequency, i.e. the reference dataset is extended by constant values.
An enhancement label is used to mark the different levels of measurement accuracy. This
enhancement label is displayed at the right diagram border if normalization is switched on and a
deviation from the reference setting occurs. Three accuracy levels are defined:
Table 4-8: Measurement accuracy levels
Accuracy Enhancement label Reason/Limitation
high NOR no difference between reference setting and measurement
medium APX (approximation) change of the following settings:
coupling (RBW, VBW, SWT)
reference level, RF attenuation
start or stop frequency
output level of tracking generator
detector (max. peak, min. peak, sample, etc.)
change of frequency:
max. 501 points within the set sweep limits (corresponds to a doubling of the span)
– Aborted normalization more than 500 extrapolated points within the current sweep limits (in case of span
doubling)
Note: At a reference level of –10 dBm and at a tracking generator output level of the same value the
R&S FSL operates without overrange reserve, i.e. the R&S FSL is in danger of being
overloaded if a signal is applied whose amplitude is higher than the reference line. In this case,
either the message OVLD for overload or IFOVL for exceeded display range (clipping of the
trace at the upper diagram border = overrange) is displayed in the status line.
Overloading can be avoided as follows:
• Reducing the output level of the tracking generator (Source Power softkey in the tracking
generator menu)
• Increasing the reference level (Ref Level softkey in the amplitude menu)
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